A major goal of this research is to continue with the characterization of the protein of isolated and purified photoreceptor complexes and reaction center complexes prepared from photosynthetic bacteria, particularly those from R. rubrum. We plan to determine the amino acid sequence of one of the major polypeptides (an organic solvent soluble polypeptide) which we have isolated in large quantities in pure form from R. rubrum. We will also look for isolation procedures to purify large quantities of the other polypeptide(s) of the photoreceptor complex. Since an organic solvent soluble polypeptide(s) (OSSP) is easily isolated from each photosynthetic bacteria so far studied, much might be learned by comparing the amino acid sequence of several of these. If, as with other proteins, once the first member of a class is sequenced, it may become much easier to sequence other members of the class or at least compare parts of their sequences. Further characterization of the photoreceptor complex from R. rubrum will continue. The next goals are to: a) determine the functional role of OSSP; b) separate the phototrap from the antenna complex and isolate the polypeptides of the phototrap in sufficient quantities for characterization and eventual sequence determination work; c) further clarify the relationship between ubiquinone and the primary photochemical event. Reconstitution of activity experiments will be conducted at two levels: 1) Generation of a photoreceptor complex from the purified components (pigments, polypeptides, ubiquinone, etc.). 2) Restoration of photophosphorylation activity to selectively depleted chromatophores.